Computer components such as high powered integrated circuit modules are generating increasing amounts of heat. Unless the heat is effectively dissipated, it can cause the modules to malfunction. A common technique to enhance the heat transferal from such a component is to increase the surface area from which the heat is transferred. One method, typical in many industrial applications, is to attach a parallel fin heat sink to such a component. Forced air is then often ducted to the parallel fin heat sink from an air moving device. An assembly such as this composed of an air moving device, ducting, and a heat sink can devour significant space within the overall hardware system and cause excessive noise.
Typically the gas/solid interface for a heat sink is the controlling resistance to heat transferred from a parallel fin heat sink. As air passes along the length of the fins, a thermal boundary layer grows on each fin acting as the resistance to heat flow from the fin. In addition, the temperature of the air rises as it passes the length of the heat sink as a result of the increased heat being dissipated to the air. Finally, since the fin has a higher efficiency in dissipating heat nearer the base the air temperature at this location is higher, again acting as a higher resistance to heat flowing from the fin.
In a design utilizing a finned heat sink it is desirable to duct air directly to the heat sink to maximize the heat transfer capability of the heat sink. However, many heat sink designs are not ducted and thus permit air flow to migrate out the top or around the sides of the heat sink. This gives rise to diminished flow within the fins and increases the resistance to heat flow at the gas/solid interface, thereby limiting the effectiveness of the heat sink design.
To provide greater air flow to the heat sink, some previous art has utilized piezoelectric fan blades. For example, Asia patent application, 1-233796, filed Sep. 19, 1989, teaches a parallel finned heat sink with piezoelectric fan blades interspersed within the fins. The blades vibrate to dissipate the heat from the fins of the heat sink. Similarly, U.S. patent 4,923,000, issued Mar. 3, 1989 to Richard D. Nelson deals with piezoelectric blades positioned between the fins of a fluid heat exchanger having a fluid inlet and outlet. Neither of these piezoelectric fan applications provide for the high velocity air flow to furnish efficient cooling. Other prior ad has utilized rotational means to achieve air flow. An illustration is U.S. Pat. No. 4,144,932, issued Jun. 2, 1977 to James R. Voigt, which deals with a heat generating component mounted to one side of a disk and fins on the other side. The disk has openings so that when the disk is rotated air flows through. Voigt's teachings only apply to circuits mounted on a rotating disk, not a fixed module.
Thus the prior art lacks the capacity to provide high velocity air flow in order to adequately cool both fixed finned heat sinks and components mounted on a printed circuit card. There exists, therefore, a need to improve the heat transfer characteristics of a parallel fin heat sink and at the same time provide an assembly that will significantly reduce the space required to provide the desired thermal performance. This embodiment presents a novel design of a parallel fin heat sink integrated with a "disk fan" to provide improved heat transfer characteristics and at the same time improved packaging density with reduced noise.